A proportional variable force solenoid control valve that is relative low in cost to manufacture and compact in size while maintaining substantially linear proportional fluid control is described in the Najmolhoda U.S. Pat. No. 4,988,074.
The proportional variable force control valve includes a ferromagnetic (e.g. steel) armature suspended by low spring rate springs at opposite ends of the armature within the bore hole of a coreless solenoid bobbin for reciprocable movement between a first valve position and a second valve position in response to applied electrical current to an electromagnetic coil. The position of the armature is controlled by balancing the variable force of an electromagnetic field of an electromagnetic coil and the force of the magnetic field of a permanent ring magnet against the force of a compression coil spring which biases the valve toward the closed position of the valve. The electromagnetic coil, bobbin and armature reside in a solenoid housing. The fluid control valve on the end of the armature moves relative to a valve seat disposed in the valve housing to communicate a fluid inlet to fluid exhaust ports so as to regulate fluid pressure at fluid control ports in a manner proportional to the magnitude of applied electrical current.
A commercially manufactured version of the aforementioned patented proportional variable force solenoid fluid control valve has been modified to include a stainless steel ball valve and a separate stainless steel valve seat insert pressed in the nozzle. The ball valve is captured in a stainless steel cage between the valve seat and a rod-like, cylindrical shaped steel armature that moves relative to the valve seat in a manner proportional to the magnitude of electrical current applied to the electromagnetic coil. As the armature moves relative to the valve seat to actuate the valve, the ball valve is caused to follow the end of the armature by virtue of fluid pressure in the valve member housing and confinement in the ball valve cage in the bobbin. The fluid inlet is communicated to fluid exhaust ports by opening of the ball valve so as to regulate fluid pressure at fluid control ports in a manner proportional to the magnitude of electrical current applied to the coil.
A spool valve is disposed in the valve member housing for providing a two stage, high flow capability wherein pressurized fluid supplied to the inlet port initially is directed to bypass the control ports and flows to an end of the spool valve to move it from a zero fluid flow spool position to a maximum fluid flow spool position relative to the control ports as determined by the cracking pressure preset for the ball valve by adjustment of the coil spring force. Thereafter, a second stage of operation involves controlling the fluid flow through the control ports by moving the spool valve between minimum and maximum flow spool positions in a manner proportional to the magnitude of electrical current to the coil.
The Najmolhoda U.S. Pat. No. 5,984,259 describes a proportional variable force solenoid control valve that includes a damping member connected to or part of the armature to provide improved valve response stability to noise in the controlled fluid system, especially in use in an electronically controlled hydraulic automatic transmission application.
Variable cam phase adjustment mechanisms are known for changing the timing of the valve train of an internal combustion engine. Such cam phasing systems have used high flow, 4 port VBS variable bleed solenoids that generally utilize a direct acting spool and armature subassembly due the complex hydraulic porting required for 2 control ports. Such designs have very low output forces and can be susceptible to friction/lodging due to contaminants. A direct acting (single stage) 4-way solenoid operated valve for use with a cam phasing mechanism is described in U.S. Pat. No. 6,640,834. Such designs have very low output forces as a result of direct action of the armature on the spring-biased spool and can be susceptible to friction/lodging due to contaminants.